Operation Method of Storage Device

1. An operation method of a storage device connected to a host, the method comprising: fetching a plurality of first commands from a first submission queue of the host by performing a first command fetch operation, the plurality of first commands including a first fused command and not including a second fused command; when a last command among the plurality of first commands is the first fused command, processing one or more remaining commands of the plurality of first commands other than the last command; fetching one or more second commands from a second submission queue of the host by performing a second command fetch operation; processing the one or more second commands; and fetching at least two third commands from the first submission queue of the host by performing a third command fetch operation, wherein the at least two third commands include the first fused command and the second fused command corresponding to the first fused command.

2. The method of claim 1, wherein the first fused command is a compare command and the second fused command is a write command.

3. The method of claim 2, further comprising: performing a fused operation of compare and write by processing the first fused command and the second fused command in an atomic unit.

4. The method of claim 1, wherein the processing of the one or more remaining commands includes: checking a fused operation (FUSE) field of the last command among the plurality of first commands; and when the FUSE field of the last command indicates that the last command is the first fused command, discarding the last command.

5. The method of claim 4, wherein the processing of the one or more remaining commands further includes: when the FUSE field of the last command indicates that the last command is the first fused command, updating a head pointer of the first submission queue such that the head pointer points out the last command.

6. The method of claim 4, wherein the checking of the FUSE field of the last command is performed before the last command is parsed.

7. The method of claim 1, wherein the processing of the one or more remaining commands includes: when a pending command is absent from the first submission queue of the host, reporting an error associated with the last command to the host.

8. The method of claim 7, wherein the processing of the one or more remaining commands further includes: when the pending command is absent from the first submission queue of the host, updating a head pointer of the first submission queue such that the head pointer points out a position of a tail pointer of the first submission queue.

9. The method of claim 1, wherein the number of the plurality of first commands fetched from the first submission queue through the first command fetch operation is “N”, wherein Nis a natural number, and wherein the number of the at least two third commands fetched from the first submission queue through the third command fetch operation is (N+1).

10. The method of claim 1, wherein the last command is a command, which is the closest in position to a tail pointer of the first submission queue, from among the plurality of first commands.

11. The method of claim 1, wherein the fetching of the plurality of first commands from the first submission queue includes: selecting the first submission queue among a plurality of submission queues of the host, based on an arbitration policy, wherein the fetching of the one or more second commands from the second submission queue includes: selecting the second submission queue among the plurality of submission queues of the host, based on the arbitration policy, and wherein the fetching of the at least two third commands from the first submission queue includes: selecting the first submission queue among the plurality of submission queues of the host, based on the arbitration policy.

12. The method of claim 11, wherein the arbitration policy is one of a round-robin policy and a weighted round-robin policy for the plurality of submission queues.

13. An operation method of a storage device connected to a host, the method comprising: fetching N commands (N being a natural number greater than 1) from a first submission queue of the host by performing a first command fetch operation, the N commands including a first fused command and not including a second fused command; and fetching M commands (M being a natural number) from a second submission queue of the host by performing a second command fetch operation, wherein the performing of the first command fetch operation includes: before the performing of the second command fetch operation, when a fused operation (FUSE) field of a last command among the N commands fetched from the first submission queue through the first command fetch operation includes a first value, selectively further fetching a next command from the first submission queue, and wherein the last command and the next command are processed in an atomic unit.

14. The method of claim 13, wherein the last command is a compare command and the next command is a write command.

15. The method of claim 13, further comprising: after further fetching the next command from the first submission queue, updating a head pointer of the first submission queue such that the head pointer points out a position following the next command in the first submission queue.

16. The method of claim 13, further comprising: fetching (N−1) commands from the first submission queue of the host by performing a third command fetch operation; and fetching M commands from the second submission queue of the host by performing a fourth command fetch operation.

17. The method of claim 16, wherein the “N” and the “M” are decided based on an internal arbitration policy of the storage device.

18. An operation method of a storage device which is connected to a host, the method comprising: performing a fused operation in response to a first fused command and a second fused command written in a first submission queue of the host, wherein the performing of the fused operation includes: fetching a plurality of first commands from the first submission queue by performing a first command fetch operation, wherein the plurality of first commands include the first fused command and do not include the second fused command; processing one or more remaining commands among the plurality of first commands other than the first fused command; fetching a plurality of second commands from the first submission queue, wherein the plurality of second commands include both the first fused command and the second fused command; and processing the plurality of second commands, wherein the first and second fused commands are processed in an atomic unit.

19. The method of claim 18, wherein the processing of the one or more remaining commands includes: determining whether a last command among the plurality of first commands is the first fused command, based on a fused operation (FUSE) field of the last command; and when the last command is the first fused command, processing the one or more remaining commands other than the first fused command among the plurality of first commands.

20. The method of claim 18, wherein the processing of the one or more remaining commands includes: determining whether a last command among the plurality of first commands is the first fused command, based on a fused operation (FUSE) field of the last command; and when the last command is the first fused command, updating a head pointer of the first submission queue such that the head pointer points out a position of the last command.